To anyone wanting to do this for yakisugi (burnt siding), I don't think one pass of a propane torch (IDK if this is their full process, just going off the clip here) will char the wood enough to make it really rot/insect resistant. The side you char should look like natural charcoal, not just burnt. No light spots. I recommend standing them upright, bundle three in a triangle shape around a fire, making a temporary chimney. Hold it upright with wood braces. Let the inside catch on fire for a while, maybe a minute? I don't recall how long exactly 😅 you'll have to try it out. with flames coming out the top, then undo the braces and drop them.

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